Liquid cooling module

ABSTRACT

A liquid cooling module includes a heat-receiver, an inlet-passage in which a flow-path through which the liquid-refrigerant flowed from an inlet flows is formed, a first flow-passage in which the flow-path continues from the inlet-passage, and that is formed as spreading in a fan-like shape as viewed in a normal-direction of a heat-receiving-surface, a second flow-passage in which the flow-path continues from the first flow-passage, and that is formed toward the heat-receiver in the normal-direction, a diffuser in which grooves that continue from the second flow-passage in the heat-receiver and diffuses the liquid-refrigerant along a surface on an opposite side of the heat-receiving-surface is formed, a third flow-passage in which the flow-path continues from the grooves, and that is formed in the normal-direction and a direction in which the flow-path is separating from the heat-receiver, and an outlet-passage in which the flow-path continues from the third flow-passage to an outlet.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2022-62552, filed on Apr. 4, 2022,the entire contents of which are incorporated herein by reference.

FIELD

The technology disclosed in the present application is related to aliquid cooling module.

BACKGROUND

There is a structure in which a cooling block is arranged on a backsurface side of a heat element chip, cools the heat element chip, andkeeps a semiconductor element temperature in the chip at a fixedtemperature. In this structure, a part of a flow quantity of refrigerantliquid flowing in a main flow passage pipe is branched with arefrigerant liquid branching mechanism having a pipe structure and isguided to the side of the heat element chip of the cooling block. In asurface on a side of the cooling block that has contact with the heatelement chip, cooling fins are arranged in parallel or radially, and therefrigerant liquid flows between the fins. At this time, the refrigerantliquid removes heat generated in the heat element chip via phosphorusand is heated.

Furthermore, there is a structure in which a semiconductor element suchas a central processing unit (CPU) and a cooling plate are configured tobe in close thermal contact with each other, partition plates form aflow passage in the cooling plate in a state where the partition plateson both ends are provided on one side of the pipe side and remainingpartition plates are arranged in a staggered manner. In this structure,a suction pipe and a discharge pipe are disposed on one side of thecooling plate, a space for the pipes is not needed on the front and rearsides of the cooling plate due to high-density mounting components, andthe pipes can be compactly accommodated.

Japanese Laid-open Patent Publication No. 1-111362 and JapaneseLaid-open Patent Publication No. 2006-73881 are disclosed as relatedart.

SUMMARY

According to an aspect of the embodiments, a liquid cooling moduleincludes a heat receiver that includes a heat receiving surface thatreceives heat of a cooling target, an inlet passage that includes aninlet into which a liquid refrigerant that exchanges heat in the heatreceiver flows, and in which a flow path through which the liquidrefrigerant flowed from the inlet flows is formed, a first flow passagein which the flow path continues from the inlet passage, and that isformed as spreading in a fan-like shape as viewed in a normal directionof the heat receiving surface, a second flow passage in which the flowpath continues from the first flow passage, and that is formed towardthe heat receiver in the normal direction, a diffuser in which aplurality of grooves that continues from the flow path of the secondflow passage in the heat receiver and diffuses the liquid refrigerantalong a surface on an opposite side of the heat receiving surface isformed, a third flow passage in which the flow path continues from theplurality of grooves, and that is formed in the normal direction and adirection in which the flow path is separating from the heat receiver,and an outlet passage that includes an outlet that flows out the liquidrefrigerant, and in which the flow path continues from the third flowpassage to the outlet, wherein the flow path at the inlet passage andthe flow path at the outlet passage are at same height positions fromthe heat receiving surface.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of an electronic device including a liquid coolingmodule according to one embodiment of the technology disclosed in thepresent application;

FIG. 2 is a perspective view illustrating the liquid cooling moduleaccording to one embodiment of the technology disclosed in the presentapplication;

FIG. 3 is an exploded perspective view illustrating the liquid coolingmodule according to one embodiment of the technology disclosed in thepresent application;

FIG. 4 is a plan cross-sectional view illustrating the liquid coolingmodule according to one embodiment of the technology disclosed in thepresent application;

FIG. 5 is a cross-sectional view taken along a line 5-5 in FIG. 4illustrating the liquid cooling module according to one embodiment ofthe technology disclosed in the present application; and

FIG. 6 is a cross-sectional view taken along a line 6-6 in FIG. 4illustrating the liquid cooling module according to one embodiment ofthe technology disclosed in the present application.

DESCRIPTION OF EMBODIMENTS

A liquid cooling module cools an electronic component that is a coolingtarget through heat transfer to a liquid refrigerant. In an electronicdevice including such a liquid cooling module therein, there is a casewhere a height is limited. For example, as the liquid cooling module, itis required to secure a cooling performance and reduce the height.

Hereinafter, embodiments of technologies capable to secure the coolingperformance of the liquid cooling module and reduce the height will bedescribed in detail with reference to the drawings.

EMBODIMENTS

In FIG. 1 , an electronic device 10 including a liquid cooling module 30according to one embodiment of the technology disclosed in the presentapplication is illustrated in planar view. The electronic device 10includes a housing 12 as illustrated in FIG. 1 . The housing 12 is arectangular box-like member, as an example. The front side in thefront-back direction of the electronic device 10 is indicated by anarrow FR, the right side in the width direction is indicated by an arrowRH, and the upper side in the height direction is indicated by an arrowUP. The electronic device 10 is, for example, a server, and for example,a rack mount server. The rack mount server is mounted on a rack in aposture in which a height direction of the rack mount server is thevertical direction.

An auxiliary storage device such as a hard disk drive (HDD) 16 ismounted on the front side in the housing 12. A fan 18 is mounted on therear side of the HDD 16. Moreover, on the rear side of the fan 18, amain storage device such as a dual inline memory module (DIMM) 20 and aprocessor (processing device) such as a central processing unit (CPU) 22are arranged side by side in the width direction. The CPU 22 and theDIMM 20 are mounted on a board 14 (refer to FIGS. 5 and 6 ) or the like.

In the example illustrated in FIG. 1 , the number of CPUs 22 is two. Thetwo corresponding DIMMs 20 are arranged on each of both sides in thewidth direction for each CPU 22. Each CPU 22 and the corresponding DIMMs20 on the both sides are electrically connected, for example, with awiring pattern or the like on the board 14 and exchange electricalsignals.

The CPU 22 is an example of a “cooling target” according to thetechnology of the present disclosure. Using the CPU 22 as a reference,the fan 18 is positioned on the front side of the CPU 22, and the DIMMs20 are positioned on both of the left and right sides in the widthdirection.

By driving the fan 18, wind in a direction indicated by an arrow F1 inFIG. 1 , for example, an airflow is generated. This wind cools the DIMM20. The DIMM 20 is an example of a “second cooling target” according tothe technology of the present disclosure.

A connection device such as a peripheral component interconnect (PCI) 24and a power supply device such as a power supply unit (PSU) 26 aremounted on the rear side in the housing 12.

The liquid cooling module 30 illustrated in FIGS. 2 to 6 is providedcorresponding to each CPU 22 and cools the CPU 22 by receiving heat ofthe CPU 22. In the present embodiment, since the number of CPUs 22 istwo, the two liquid cooling modules 30 are provided. Hereinafter, in acase where the two liquid cooling modules 30 are distinguished from eachother, the two liquid cooling modules 30 are distinguished as a liquidcooling module 30L on the left side in the width direction and a liquidcooling module 30R on the right side in the width direction. In eitherof the two liquid cooling modules 30, the CPU 22 overlaps at the centerposition of the liquid cooling module 30 in planar view, for example, asviewed in the normal direction of a heat receiving surface 48 to bedescribed later. In the present embodiment, the normal direction of theheat receiving surface 48 is also the height direction of the liquidcooling module 30.

In the present embodiment, the front-back direction, the widthdirection, and the depth direction of the liquid cooling module 30respectively match the front-back direction, the width direction, andthe depth direction of the electronic device 10. Therefore, the arrowFR, the arrow RH, and the arrow UP in FIGS. 2 to 6 respectively indicatethe front side in the front-back direction, the right side in the widthdirection, and the upper side in the vertical direction of the liquidcooling module 30.

As illustrated in FIGS. 2 and 3 , the liquid cooling module 30 includesa cold plate 32. As illustrated in FIG. 3 , the cold plate 32 includes abase 34, a cover 36, and a flow passage block 38.

The base 34 is a plate-like member, and for example, at each of fourcorners, the base 34 is fixed to the board 14 or the like with afastener 40.

The flow passage block 38 is a member on which recesses and holesforming a flow path FP having a predetermined shape as described laterand is mounted on the base 34.

The cover 36 is a box-like member of which a lower surface side opens.The cover 36 is fixed to the base 34 in a state of covering a topsurface, a right side surface, a left side surface, a front surface, anda rear surface of the flow passage block 38 mounted on the base 34. In aportion of the flow passage block 38 where a recess portion is formed,the recess portion forms the flow path FP by covering the flow passageblock 38 with the cover 36 in this way. Note that the flow passage block38 and the cover 36 have shapes that do not interfere with the fasteners40.

On the rear side of the cold plate 32, a convex portion 42 projectedbackward in a convex manner is formed at the center in the widthdirection. A rear surface of the convex portion 42 is an opening surface44. In the opening surface 44, an inlet 54 and an outlet 68 are openedas described later.

As illustrated in FIGS. 5 and 6 , a lower portion of the liquid coolingmodule 30 is a heat receiving portion 46. The heat receiving portion 46includes the heat receiving surface 48 on the lower surface of the base34. The heat receiving surface 48 is arranged on the top surface of theCPU 22 via a heat transfer member 50 such as a heat transfer sheet or agrease. The heat receiving surface 48 is a surface that receives heat ofthe CPU 22.

The liquid cooling module 30 includes an inlet portion (inlet passage)52, a first flow passage portion 56, a second flow passage portion 58, adiffusion portion 60, a third flow passage portion 64, and an outletportion (outlet passage) 66 in the cold plate 32. Then, in the liquidcooling module 30, the flow path FP is formed in which a liquid coolingrefrigerant flows in order of the inlet portion 52, the first flowpassage portion 56, the second flow passage portion 58, the diffusionportion 60, the third flow passage portion 64, and the outlet portion66.

The inlet portion 52 and the outlet portion 66 are positioned on theupper portion of the cold plate 32, in the cold plate 32.

The inlet portion 52 includes the opening inlet 54 on the openingsurface 44. A pipe 72 is connected to the inlet 54 via a connector 80.As illustrated in FIG. 3 , the inlet 54 is continuous with the flow pathFP at the inlet portion 52 of the flow passage block 38.

As illustrated in FIGS. 3 and 4 , the flow path FP at the inlet portion52 has a shape that extends forward from the inlet 54, curves leftwardin the width direction in the middle, and curves forward, and inaddition, curves rightward in the width direction. Then, the flow pathFP at the inlet portion 52 is parallel to the heat receiving surface 48(refer to FIG. 5 ) over the entire length.

As illustrated in FIGS. 3 to 5 , the flow path FP at the first flowpassage portion 56 is continuous with the flow path FP at the inletportion 52. The flow path FP at the first flow passage portion 56 has ashape that spreads out in a fan-like shape from the front end of theflow path FP on the side of the inlet portion 52, in planar view, forexample, as viewed in the normal direction of the heat receiving surface48.

This “fan-like shape” indicates a shape that spreads leftward andrightward with respect to the center on the downstream side in the flowof the refrigerant flowed from the flow path FP at the inlet portion 52.In the example illustrated in FIG. 4 , the flow path FP at the firstflow passage portion 56 has a shape that spreads in the front-backdirection from the left side in the width direction toward the rightside in the width direction. This flow path FP having the fan-like shapeis positioned at the center in the front-back direction and the centerin the width direction of the liquid cooling module 30, in planar view.

Furthermore, as illustrated in FIG. 5 , a bottom surface 56B of the flowpath FP at the first flow passage portion 56 is inclined toward adirection away from the heat receiving surface 48, for example, upward,from the left side in the width direction toward the right side in thewidth direction. An inclination angle θ at which the bottom surface 56Bof the flow path FP at the first flow passage portion 56 is inclined isfixed at any position in the flow path FP at the first flow passageportion 56. This inclination angle θ is an angle of the bottom surface56B of the flow path FP with respect to a surface PP parallel to theheat receiving surface 48. Furthermore, the bottom surface 56B of theflow path FP at the first flow passage portion 56 is not inclined in thedirection in which the fan-like shape spreads, for example, thefront-back direction of the liquid cooling module 30.

A length of an inclined portion of the bottom surface 56B of the flowpath FP at the first flow passage portion 56 is longer at the center ofthe fan-like shape and is shorter on both sides of the fan-like shape(both sides in front-back direction of liquid cooling module 30). Forexample, when the flow path FP at the first flow passage portion 56 inthe cross section illustrated in FIG. 5 is compared with the flow pathFP at the first flow passage portion 56 in the cross section illustratedin FIG. 6 , the flow path FP illustrated in FIG. 5 is longer.

From the front end portion of the flow path FP at the first flow passageportion 56, the flow path FP at the second flow passage portion 58continues. The flow path FP at the second flow passage portion 58 isformed toward the heat receiving portion 46, for example, downward.

As illustrated in FIG. 4 , the flow path FP at the second flow passageportion 58 has an opening length same as the flow path FP at the firstflow passage portion 56, in the front-back direction of the liquidcooling module 30. On the other hand, in the width direction of theliquid cooling module 30, the flow path FP has an opening width shorterthan, for example, an inner diameter of the flow path FP of the inletportion 52 (opening length in width direction of liquid cooling module30). Then, the opening width of the flow path FP at the second flowpassage portion 58 is gradually narrowed from the center toward bothends in the front-back direction.

The diffusion portion 60 is provided in the heat receiving portion 46.On the top surface of the base 34, for example, a surface on theopposite side of the heat receiving surface, a plurality of grooves 62continuous from the flow path FP at the second flow passage portion 58is formed. The flow path FP at the diffusion portion 60 has amicrochannel structure that diffuses the refrigerant with the pluralityof grooves 62 in this way. For example, each of the plurality of grooves62 extends in the width direction of the cold plate 32, and theseplurality of grooves 62 spreads the liquid refrigerant in the widthdirection. Furthermore, the plurality of grooves 62 is formed at regularintervals (pitch) in the front-back direction of the cold plate 32. Aportion where the groove 62 is formed is in a range same as the flowpath FP at the second flow passage portion 58, in the front-backdirection of the cold plate 32. As a result, the refrigerant that flowsthrough the flow path FP at the second flow passage portion 58 flowsinto any one of the plurality of grooves 62 and is diffused in the widthdirection. The interior of the groove 62 also form a part of the flowpath FP of the refrigerant.

A cross-sectional area of the flow path FP for all of the plurality ofgrooves 62 is set, for example, to be smaller than the flow path FP atthe inlet portion 52 and further to be smaller than a cross-sectionalarea of the flow path FP at the second flow passage portion 58.Therefore, for example, as compared with a structure of which thecross-sectional area of the flow path FP for all of the plurality ofgrooves 62 is larger than the cross-sectional area of the flow path FPat the second flow passage portion 58, a flow velocity of therefrigerant flowing through the groove 62 increases.

From the diffusion portion 60, the flow path FP at the third flowpassage portion 64 continues. The flow path FP at the third flow passageportion 64 is formed in a direction in which the flow path FP isseparating from the heat receiving portion 46, for example, upward.

In the present embodiment, a plurality of the flow passages FP at thethird flow passage portion 64 is provided. In the example illustrated inFIG. 6 , the two flow passages FP at the third flow passage portion 64are provided with an interval in the width direction. Hereinafter, theflow passages FP at the third flow passage portion 64 are appropriatelydistinguished from each other as a flow path FPR that is a flow passageon the right side in the width direction and a flow path FPL that is aflow passage on the left side in the width direction. The flow path FPRon the right side in the width direction is formed upward from aposition at an end of the groove 62 on the right side in the widthdirection, and the flow path FPL on the left side in the width directionis formed upward from a position at an end of the groove 62 on the leftside in the width direction.

The flow path FP at the outlet portion 66 is continuous from the flowpath FPR on the right side in the width direction of the third flowpassage portion 64. For example, the flow path FP at the outlet portion66 is formed forward from the flow path FPR, further formed to be curvedrightward in the width direction, and further to be curved rearward.Then, to the middle of the portion formed rearward in this way, the flowpath FPR on the left side in the width direction of the third flowpassage portion 64 joins.

The flow path FP at the outlet portion 66 is curved leftward in thewidth direction and is curved rearward again, from the portion formedrearward. The flow path FP at the outlet portion 66 is parallel to theheat receiving surface 48 over the entire length.

As illustrated in FIG. 3 , the outlet portion 66 includes the openingoutlet 68 on the opening surface 44. The outlet 68 is continuous withthe flow path FP at the outlet portion 66 of the flow passage block 38.The pipe 72 is connected to the outlet 68 via the connector 80,similarly to the inlet 54. The pipe 72 connected to the inlet 54 and thepipe 72 connected to the outlet 68 are parallel to each other at aconnected portion to the inlet 54 and a connected portion to the outlet68.

As illustrated in FIG. 3 , a height position from the heat receivingsurface 48, for example, a position in the vertical direction of theliquid cooling module 30 of the flow path FP at the outlet portion 66 isthe same height position as the flow path FP at the inlet portion 52over the entire length. The height position from the heat receivingsurface 48 is also a position in the normal direction of the heatreceiving surface 48.

Here, the fact that the heights from the heat receiving surface 48 arethe “same” indicates that the flow path FP at the inlet portion 52 andthe flow path FP at the outlet portion 66 partially or entirely overlapin the height direction when viewing the liquid cooling module 30 in thewidth direction. For example, in the example illustrated in FIG. 5 , theflow path FP at the inlet portion 52 and the flow path FP at the outletportion 66 have the same cross-sectional shape, and the center of theopening portion of the inlet portion 52 and the center of the openingportion of the outlet portion 66 are at the same height. Then, whenviewed in the width direction, the flow path FP at the inlet portion 52and the flow path FP at the outlet portion 66 entirely overlap in theheight direction.

Furthermore, the flow path FP at the inlet portion 52 and the flow pathFP at the outlet portion 66 have the same height from the heat receivingsurface 48, with respect to the flow path FP at the first flow passageportion 56. Then, as illustrated in FIG. 4 , the flow path FP at theinlet portion 52 and the flow path FP at the outlet portion 66 arearranged at positions avoiding the flow path FP at the first flowpassage portion 56, in planar view. For example, the flow path FP at thefirst flow passage portion 56 is arranged at the center of the liquidcooling module 30, whereas the flow path FP at the inlet portion 52 andthe flow path FP at the outlet portion 66 are arranged along an outerperiphery of the liquid cooling module 30. A part of the flow path FP atthe inlet portion 52 and a part of the flow path FP at the outletportion 66 surround the flow path FP at the first flow passage portion56 (fan-like shape flow path FP), in planar view.

In the entire liquid cooling module 30, the flow path FP of therefrigerant is folded from the front side toward the rear side in theliquid cooling module 30 between a position where the refrigerant isintroduced from the inlet 54 and a position where the refrigerant isdischarged from the outlet 68. Then, both of the inlet 54 and the outlet68 are formed on the opening surface 44.

In this way, the flow path FP in the cold plate 32 has a portion that isformed in all of the depth direction, the width direction, and theheight direction and has a three-dimensional structure.

As illustrated in FIG. 3 , the inlet 54 and the outlet 68 open into theopening surface 44 of the liquid cooling module 30. Furthermore, theinlet 54 and the outlet 68 have the same height positions from the heatreceiving surface 48.

As illustrated in FIG. 1 , the pipe 72 connected to the inlet 54 of theliquid cooling module 30R on the right side in the width direction actsas an introduction pipe 74. The refrigerant is introduced from outsideof the electronic device 10 into the liquid cooling module 30R throughthe introduction pipe 74.

The pipe 72 connected to the outlet 68 of the liquid cooling module 30Lacts as a discharge pipe 78. The liquid refrigerant in the liquidcooling module 30L is discharged to the outside of the electronic device10 through the discharge pipe 78.

The pipe 72 connects between the outlet 68 of the liquid cooling module30R on the right side in the width direction and the inlet 54 of theliquid cooling module 30L, and this pipe 72 acts as a transfer pipe 76.The liquid refrigerant is discharged from the outlet 68 of the liquidcooling module 30R through the transfer pipe 76, sent to the inlet 54 ofthe liquid cooling module 30L, and introduced into the liquid coolingmodule 30L. The transfer pipe 76 functions as a discharge pipe for theliquid cooling module 30R and functions as an introduction pipe for theliquid cooling module 30L.

Both of the liquid cooling module 30R and the liquid cooling module 30Lare arranged in a direction in which the opening surface 44 facesrearward. All of the introduction pipe 74, the transfer pipe 76, and thedischarge pipe 78 are arranged on the rear side without passing throughthe front side of the liquid cooling module 30R and the liquid coolingmodule 30L. For example, the introduction pipe 74, the transfer pipe 76,and the discharge pipe 78 are arranged to avoid a range between the fan18 and the DIMM 20.

Next, actions of the present embodiment will be described.

A liquid refrigerant is introduced into the liquid cooling module 30,from the inlet 54. This refrigerant flows from the flow path FP at theinlet portion 52 toward the flow path FP at the first flow passageportion 56, in the liquid cooling module 30. The flow path FP at thefirst flow passage portion 56 has a fan-like shape, and the refrigerantspreads in the front-back direction along the shape of the flow path FPat the first flow passage portion 56. Moreover, the refrigerant flowsthrough the flow path FP at the second flow passage portion 58. Sincethe flow path FP at the second flow passage portion 58 extends towardthe heat receiving surface 48, the refrigerant flows toward the heatreceiving surface 48.

Moreover, the refrigerant flows through the flow path FP at thediffusion portion 60. Since the flow path FP at the diffusion portion 60has the plurality of grooves 62, the refrigerant flows into any one ofthe plurality of grooves 62 and flows as spreading in the widthdirection. Therefore, the refrigerant is diffused in the front-backdirection and the width direction, in the diffusion portion 60. Sincethe diffusion portion 60 is provided in the heat receiving portion 46,the heat of the CPU 22 is transferred to the refrigerant via the heatreceiving portion 46, and the CPU 22 is cooled.

Then, the refrigerant flows in a direction away from the heat receivingportion 46, through the flow path FP at the third flow passage portion64. Moreover, the refrigerant flows through the flow path FP at theoutlet portion 66 and is discharged to the outside of the liquid coolingmodule 30 from the outlet 68.

In this way, the refrigerant is diffused in the front-back direction andthe width direction, in the heat receiving portion 46 of the liquidcooling module 30. Therefore, as compared with a structure in which therefrigerant is not diffused, it is possible to more efficiently receivethe heat of the CPU 22 by the refrigerant. For example, as compared witha cooling device that cools the CPU 22 using cooling wind, that is, aso-called air-cooling cooling device, in the present embodiment, it ispossible to efficiently cool the cooling target through liquid-cooling.

In the present embodiment, the flow path FP of the refrigerant is foldedafter the refrigerant is diffused with the flow path FP at the diffusionportion 60, in the liquid cooling module 30. For example, although adirection in which the refrigerant flows from the inlet 54 on the rearsurface is a front side, the flow path FP has a structure that is foldedrearward in the liquid cooling module 30 and in which the refrigerantflows out from the outlet 68 on the rear surface side. By folding theflow path FP in this way, a structure is realized in which the inlet 54and the outlet 68 can be formed on the same surface, for example, theopening surface 44.

The flow path FP at the inlet portion 52 and the flow path FP at theoutlet portion 66 have the same height position from the heat receivingsurface 48. On the other hand, in a structure in which the flow path FPat the inlet portion 52 and the flow path FP at the outlet portion 66have different height positions from the heat receiving surface 48, aheight occupied by the flow path FP when viewing the liquid coolingmodule 30 in the width direction increases. In the present embodiment,since the height occupied by the flow passages FP at the inlet portion52 and the outlet portion 66 is low as viewed in the width direction, aheight dimension of the liquid cooling module 30 can be reduced.

For example, in the present embodiment, the flow path FP at the inletportion 52 and the flow path FP at the outlet portion 66 entirelyoverlap in the height direction, as viewing the liquid cooling module 30in the width direction. Therefore, as compared with a structure in whichthe flow path FP at the inlet portion 52 and the flow path FP at theoutlet portion 66 partially overlap in the height direction, the heightdimension of the liquid cooling module 30 can be further reduced.

Note that, the fact that the flow path FP at the inlet portion 52 andthe flow path FP at the outlet portion 66 have the same height positionfrom the heat receiving surface 48 can be visually recognized as thatthe height positions of the inlet 54 and the outlet 68 are the same, asan appearance of the liquid cooling module 30.

In a server or the like that is an example of the electronic device 10including the liquid cooling module 30, the height of the housing 12 maybe set to be a height determined according to standards. For example, inthe rack mount server mounted on the rack, the height of the housing 12may be within a range of 1 U using 1 U=44.45 mm as a unit. In this case,it is difficult to arrange the liquid cooling module, of which theheight dimension is large, in the housing 12 having the height of 1 U.For example, in an electronic device having a structure in which variouscomponents and members are densely mounted in the housing 12, it isdifficult to secure a space where the liquid cooling module is mounted,in the housing 12.

On the other hand, the liquid cooling module 30 according to the presentembodiment can be arranged in the housing 12, for example, having theheight dimension of 1 U, by reducing the height dimension. For example,it is possible to obtain the electronic device 10 in which the housing12 with the low height dimension can implement a structure in which theCPU 22 that is the cooling target can be efficiently cooled throughliquid cooling.

In the present embodiment, both of the flow path FP at the inlet portion52 and the flow path FP at the outlet portion 66 are parallel to theheat receiving surface 48. On the other hand, for example, in astructure in which the flow path FP at the inlet portion 52 is inclinedwith respect to the heat receiving surface 48, the height of the liquidcooling module increases due to the inclination of the flow path FP.Similarly, even in a structure in which the flow path FP at the outletportion 66 is inclined with respect to the heat receiving surface 48,the height of the liquid cooling module increases due to the inclinationof the flow path FP. In the present embodiment, since the flow path FPat the inlet portion 52 and the flow path FP at the outlet portion 66are parallel to the heat receiving surface 48, the height dimension ofthe liquid cooling module 30 does not increase due to the inclination ofthe flow path FP, and it is possible to reduce the height dimension ofthe liquid cooling module 30.

Since the flow path FP at the first flow passage portion 56 spreads inthe fan-like shape, the refrigerant spreads and flows in this spreadingdirection, and retention of the refrigerant is prevented. Furthermore,the flow path FP at the first flow passage portion 56 is inclined in adirection gradually separating from the heat receiving surface 48 asspreading in the fan-like shape, for example, upward. Due to thisinclination, a resistance acts on a flow of the refrigerant that isflowing through the flow path FP at the first flow passage portion 56.Then, the length of the inclined portion of the flow path FP at thefirst flow passage portion 56 is longer at the center of the fan-likeshape, and is shorter on both sides of the fan-like shape (both sides infront-back direction of liquid cooling module 30). Therefore, theresistance with respect to the flow of the refrigerant is large at thecenter of the fan-like shape and is small on both sides of the fan-likeshape. At the center of the fan-like shape, since the refrigerant flowsstraight from the flow path FP at the inlet portion 52, a flow velocityat an initial stage of the flow increases. On the other hand, on bothsides of the fan-like shape, the flow velocity at the initial stage ofthe flow relatively decreases. However, since the inclined portion atthe center of the fan-like shape is long, the resistance of the flowmore largely acts than that on both sides. As a result, in the entireflow path FP at the first flow passage portion 56, the flow velocity ofthe refrigerant is equalized. If the flow velocity of the refrigerant islocally different, a possibility that a retention or vortex of the flowoccurs increases. However, in the present embodiment, it is possible toprevent the occurrence of the retention and the vortex of therefrigerant flowing through the flow path FP at the first flow passageportion 56.

The flow path FP at the second flow passage portion 58 is formed towardthe center of the heat receiving surface 48. Since the center of theheat receiving surface 48 is a position where the CPU 22 that is anexample of the cooling target is in contact, the heat of the CPU 22 canbe efficiently transferred to the refrigerant flowing through the flowpath FP.

The number of flow passages FP at the third flow passage portion 64 inthe present embodiment is plural (two). As compared with a structurehaving one flow path FP at the third flow passage portion 64, therefrigerant flowing through the flow path FP at the diffusion portion 60can be efficiently moved to the flow path FP at the outlet portion 66.

For example, in the present embodiment, the two flow passages FP at thethird flow passage portion 64 are the flow path FPR on the right side inthe width direction and the flow path FPL on the left side in the widthdirection. Therefore, in the diffusion portion 60, the refrigerantdiffused in the width direction can be moved from both of the right sidein the width direction and the left side in the width direction to theflow path FP at the outlet portion 66.

In the present embodiment, as illustrated in FIG. 5 , the heightposition of the flow path FP at the first flow passage portion 56 is thesame as the height positions of the flow path FP at the inlet portion 52and the flow path FP at the outlet portion 66. Therefore, as comparedwith a structure in which the height position of the flow path FP at thefirst flow passage portion 56 is different from the height positions ofthe flow path FP at the inlet portion 52 and the flow path FP at theoutlet portion 66, the height dimension of the liquid cooling module 30can be reduced.

Furthermore, the flow path FP at the inlet portion 52 and the flow pathFP at the outlet portion 66 are arranged along the outer periphery ofthe liquid cooling module 30, in planar view. As a result, a structurecan be realized in which the flow path FP at the first flow passageportion 56 can be arranged at the center of the liquid cooling module 30in planar view.

The electronic device 10 according to the present embodiment includesthe fan 18, as illustrated in FIG. 1 . Wind generated by the fan 18 cancool the DIMM 20.

The introduction pipe 74, the transfer pipe 76, and the discharge pipe78 are arranged to avoid a range between the fan 18 and the DIMM 20.Since the introduction pipe 74, the transfer pipe 76, and the dischargepipe 78 do not exist between the fan 18 and the DIMM 20, it is possibleto arrange the fan 18 and the DIMM 20 to be close to each other, and theDIMM 20 can be efficiently cooled with wind of the fan 18. Furthermore,by arranging the fan 18 and the DIMM 20 to be close to each other,various members and components can be densely arranged in the housing12.

Furthermore, the transfer pipe 76 is a pipe through which therefrigerant is discharged from the liquid cooling module 30R, and thisrefrigerant often has a higher temperature than the refrigerantintroduced into the liquid cooling module 30R. Furthermore, thedischarge pipe 78 is a pipe through which the refrigerant is dischargedfrom the liquid cooling module 30L, and this refrigerant often has ahigher temperature than the refrigerant introduced into the liquidcooling module 30R and the refrigerant introduced into the liquidcooling module 30L. In the present embodiment, since the wind generatedby the fan 18 does not pass through the transfer pipe 76 and thedischarge pipe 78 in which such a high-temperature refrigerant flows, anincrease in the temperature of the wind can be suppressed, and the DIMM20 can be efficiently cooled.

For example, in the present embodiment, the two liquid cooling modules30R and 30L, in which the inlet 54 and the outlet 68 open into the sameopening surface 44, are included. Then, the two liquid cooling modules30R and 30L are arranged so that the both of the opening surfaces 44face the same direction (rearward in example in FIG. 1 ). Therefore, astructure can be easily realized in which the outlet 68 of the liquidcooling module 30R and the inlet 54 of the liquid cooling module 30L areconnected with the transfer pipe 76 on the side where the openingsurface 44 is formed.

While one embodiment of the technology disclosed in the presentapplication has been described thus far, the technology disclosed in thepresent application is not limited to the above and, in addition to theabove, various modifications can be made without departing the spirit ofthe embodiment.

All examples and conditional language provided herein are intended forthe pedagogical purposes of aiding the reader in understanding theinvention and the concepts contributed by the inventor to further theart, and are not to be construed as limitations to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although one or more embodiments of thepresent invention have been described in detail, it should be understoodthat the various changes, substitutions, and alterations could be madehereto without departing from the spirit and scope of the invention.

What is claimed is:
 1. A liquid cooling module comprising: a heatreceiver that includes a heat receiving surface that receives heat of acooling target; an inlet passage that includes an inlet into which aliquid refrigerant that exchanges heat in the heat receiver flows, andin which a flow path through which the liquid refrigerant flowed fromthe inlet flows is formed; a first flow passage in which the flow pathcontinues from the inlet passage, and that is formed as spreading in afan-like shape as viewed in a normal direction of the heat receivingsurface; a second flow passage in which the flow path continues from thefirst flow passage, and that is formed toward the heat receiver in thenormal direction; a diffuser in which a plurality of grooves thatcontinues from the flow path of the second flow passage in the heatreceiver and diffuses the liquid refrigerant along a surface on anopposite side of the heat receiving surface is formed; a third flowpassage in which the flow path continues from the plurality of grooves,and that is formed in the normal direction and a direction in which theflow path is separating from the heat receiver; and an outlet passagethat includes an outlet that flows out the liquid refrigerant, and inwhich the flow path continues from the third flow passage to the outlet,wherein the flow path at the inlet passage and the flow path at theoutlet passage are at same height positions from the heat receivingsurface.
 2. The liquid cooling module according to claim 1, wherein theinlet and the outlet open into a same opening surface.
 3. The liquidcooling module according to claim 1, wherein the flow path of the liquidrefrigerant at the inlet passage and the flow path of the liquidrefrigerant at the outlet passage are parallel to the heat receivingsurface.
 4. The liquid cooling module according to claim 1, wherein abottom surface of the first flow passage is inclined to a direction inwhich the bottom surface is gradually separating from the heat receivingsurface as spreading in the fan-like shape.
 5. The liquid cooling moduleaccording to claim 1, wherein the flow path at the second flow passageis formed toward a center of the heat receiving surface.
 6. The liquidcooling module according to claim 1, wherein the third flow passageincludes a plurality of the flow paths.
 7. The liquid cooling moduleaccording to claim 1, wherein a height position of the flow path at thefirst flow passage from the heat receiving surface is the same as heightpositions of the flow path at the inlet passage and the flow path at theoutlet passage.
 8. An electronic device comprising: a liquid coolingmodule that includes a heat receiver that includes a heat receivingsurface that receives heat of a cooling target, an inlet passage thatincludes an inlet into which a liquid refrigerant that exchanges heat inthe heat receiving portion flows, and in which a flow path through whichthe liquid refrigerant flowed from the inlet flows is formed, a firstflow passage in which the flow path continues from the inlet passage,and that is formed as spreading in a fan-like shape as viewed in anormal direction of the heat receiving surface, a second flow passage inwhich the flow path continues from the first flow passage, and that isformed toward the heat receiving portion, a diffuser in which aplurality of grooves that continues from the flow path of the secondflow passage in the heat receiver and diffuses the liquid refrigerantalong a surface on an opposite side of the heat receiving surface isformed, a third flow passage in which the flow path continues from theplurality of grooves, and that is formed in a direction in which theflow path is separating from the heat receiver, and an outlet passagethat includes an outlet that flows out the liquid refrigerant, and inwhich the flow path continues from the third flow passage to the outlet,and wherein the flow path at the inlet passage and the flow path at theoutlet passage are at same height positions from the heat receivingsurface; and an electronic component as the cooling target to bearranged in contact with the heat receiving surface.
 9. The electronicdevice according to claim 8, further comprising: a fan configured togenerate wind that cools a second cooling target; and a pipe arranged toavoid a range between the fan and the second cooling target andconfigured to discharge the liquid refrigerant from the outlet.
 10. Theelectronic device according to claim 8, wherein the electronic deviceincludes a plurality of the liquid cooling modules, each including theinlet and the outlet that open into a same opening surface, and whereinthe plurality of liquid cooling modules is arranged with the openingsurfaces that face the same direction.